Tire vulcanizing molds are provided with vent mechanisms which discharge air left between a green tire and the mold and gas resulting from vulcanizing to the outside of the mold (see Patent Documents 1 and 2, for example). Patent Document 1 proposes a vent mechanism using a laminated blade which is a thin plate bent such that end portions on one side are superposed with each other while an end portion on the other side secures a large gap therein. This laminated blade is held by a block, and this block is fitted in a recessed pocket in the tire molding surface of the mold, thereby forming a vent chamber surrounded by the pocket and the block. Air and gas are discharged into the vent chamber through a small gap between the one end portions of the laminated blade and the large gap in the other end portion.
However, this vent mechanism requires: a step of forming the pocket in the tire molding surface of the mold after its casting; a step of making an assembly being the block holding the laminated blade; and a step of fitting this assembly into the pocket. Thus, the number of processing steps is increased, causing a problem of increased manufacturing time.
Patent Document 2 proposes a vent mechanism using a tubular body embedded in a mold at the time of casting it. A slit formed in the outer peripheral surface of the embedded tubular body is exposed at the tire molding surface of the mold, so that air and gas are discharged to the outside of the mold through this slit. According to this proposal, the processing steps can be reduced as compared to the proposal of Patent Document 1. However, to arrange the tubular body at a predetermined position on a plaster mold, the proposal of Patent Document 2 needs tubular body holding members arranged at both ends, in the tire circumferential direction, of each of pieces into which a sector is divided, and the like. Thus, there is a problem of complicating the operation of setting the tubular body on the plaster mold. Moreover, the mold needs to be cast through processes performed on a piece-by-piece basis, and hence there is a limit in improving the production efficiency.